Power magnetic devices for switching power supplies are widely used in electrical and electronic fields, such as Uninterrupted Power Supply (UPS), Active Power Filter (APF), Static Var Generator (SVG), solar inverter, power adapter, or communication power supply, etc.
Switching power supplies have a relatively high frequency, and usually employ magnetic materials such as ferrite, magnetic powder core, amorphous material, nanocrystalline, or silicon steel, etc. In many application situations, electrical and electronic products have an operation requirement for current overload, i.e. requiring an overload current of the electrical and electronic products to be larger than a rated current, sometimes up to many times higher than the rated current. For example, under an operation state when a UPS is connected with an external RCD load, the overload current is two to three times larger than the effective value of the rated current. Under such operation state, magnetic devices such as electric reactors or inductors still need to maintain a certain inductance. Thus, if the inductance of the electric reactors or inductors varies greatly as the overload current changes, the products will encounter malfunctions.
As shown in FIGS. 1A and 1B, a magnetic core structure of a conventional inductor or electric reactor includes: an upper cover plate 1 and a lower cover plate 2 which are arranged oppositely, and two wrapping posts 3 connected between the upper cover plate 1 and the lower cover plate 2. Usually, an air gap 4 is provided between each of the wrapping posts 3 and the cover plate 1 or 2, and the air gap 4 may be formed by fiberglass gasket and so on.
In the magnetic core structure of a conventional inductor or electric reactor, a cross-sectional area of the upper cover plate 1 and a cross-sectional area of the lower cover plate 2 are substantially equal to a cross-sectional area of the wrapping post 3, resulting in a poor Direct Current Bias (DC-Bias) characteristic and insufficiency in maintenance of inductance stability.
The above information disclosed in the background portion is only for the purposes of enhancing understanding of the background of the present disclosure, and thus it may include information which does not constitute prior art known to one of ordinary skill in this art.